Filter regeneration system for eliminating particulate matter generated in a diesel engine

ABSTRACT

A filter regeneration system for eliminating particulate matter generated in a diesel engine is disclosed. The filter generation system is adapted to determine a time to regenerate a filter to eliminate particulate matter discharged from the diesel engine and collected by the filter. The particulate matter is incinerated by increasing the exhaust gas temperature via an injection of fuel. The system comprises a collected amount detecting unit for detecting the amount of particulate matter collected by the filter; a control unit for determining a time to regenerate the filter based on the amount of collected particulate matter and for controlling the injection of fuel for incinerating the particulate matter; and a fuel supply unit mounted on an exhaust system for injecting the fuel in response to the control of the control unit.

FIELD OF THE INVENTION

[0001] The present invention relates to a filter regeneration system for eliminating particulate matter generated by a diesel engine. More particularly, the invention relates to a filter regeneration system adapted to accurately detect the time to regenerate for the filter used for collecting particulate matter, and to increase the discharge gas temperature via a secondary injection of fuel, and to incinerate the particulate matter collected by the filter, thereby promoting an effective regeneration of the filter.

BACKGROUND OF THE INVENTION

[0002] Generally, although a diesel engine has advantages over a gasoline engine in fuel combustion efficiency and output, the diesel engine is disadvantageous in that it creates more NOx, a hazardous material. To overcome this disadvantage, the diesel engine has adopted an exhaust gas recirculation (EGR) device for re-supplying the unburned exhaust gas to the diesel intake system, allowing the unburned exhaust gas to be re-burnt in the combustion chamber.

[0003] But there is a problem in the EGR device thus described in that, although the amount of the NOx contained in the exhaust gas after combustion can be effectively reduced, other polluting materials, such as particulate matter from the re-burning of exhaust gas, are discharged in large quantities. It has been reported that particulate matter is a major source of pollution. As a result, many efforts are being made to decrease the harmful materials, such as particulate matter. Various technologies and methods for reducing particulate matter have been developed. One such method uses a diesel particulate filtering system.

[0004] The diesel particulate filtering system is a technique by which particulate matter, discharged after combustion, is collected by a filter in an exhaust system. This matter is removed by incineration using the high temperature of the exhaust gas discharged after combustion.

[0005] Although some of the particulate matter collected by the filter is incinerated by the high temperature of the exhaust gas, there is a problem because exhaust gas discharged from the diesel engine after combustion is approximately 200° C.˜300° C. in temperature. This is much lower than the 550° C.˜600° C. temperature range necessary for completely incinerating the particulate matter.

[0006] To cope with this problem, research has been conducted to increase the temperature of exhaust gas. This has resulted in methods using a secondary injection of fuel after the main injection of fuel in a common rail engine, adding an oxidation catalyst, using fuel additives, and the like. However, these methods are all under development and are not yet practical.

[0007] The problem with the secondary injection of fuel is that it is difficult for a diesel engine particulate matter eliminating system to determine the necessary time to regenerate. There is another problem in that the control logic of a control unit becomes complicated and should precede the development of a control unit capable of performing an accurate control. Accurate control is necessary to safely control the amount of fuel injected during secondary injection for filter regeneration, even following the determination of a time to regenerate and an injection timing. There is still another problem in that even if a control unit is developed, the fuel combustion efficiency, along with the output, can be decreased by the frequency of secondary injection of fuel.

SUMMARY OF THE INVENTION

[0008] The present invention provides a filter regeneration system for eliminating particulate matter generated in a diesel engine from the filter. A preferred embodiment of the invention is adapted to accurately detect when to regenerate the filter and to inject a level of fuel adequate to incinerate the particulate matter, thereby eliminating the particulate matter collected by the filter in an effective and timely manner.

[0009] In accordance with an embodiment of the present invention, a filter regeneration system for eliminating particulate matter generated in a diesel engine from a filter comprises: a collected amount detecting unit for detecting the amount of particulate matter collected by a filter disposed in an exhaust system; a control unit for determining the time to regenerate of the filter based on the amount of collected particulate matter detected by the collected amount detecting unit and for controlling the injection of fuel for incinerating the particulate matter; and a fuel injection unit mounted on the exhaust system for injecting the fuel into the exhaust system in response to the control of the control unit.

[0010] A further preferred embodiment of the invention is a method for regenerating a filter in an exhaust system of an engine, comprising: determining when to regenerate the filter; measuring the temperature of the exhaust; and increasing the temperature of the exhaust to regenerate the filter.

[0011] Another preferred embodiment of the invention is a system for regenerating a filter in an exhaust system of an engine, comprising: a detection system for detecting filter blockage and for determining when to regenerate the filter including a pressure sensor or a flow sensor; and an exhaust temperature increasing system, including an injector for injecting a combustible material into the exhaust system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0013]FIG. 1 is a block diagram of a filter regeneration system for eliminating particulate matter generated in a diesel engine according to a preferred embodiment of the present invention; and

[0014]FIG. 2 is a schematic drawing of the system of FIG. 1.

[0015] Like numerals refer to similar elements throughout the several drawings.

DETAILED DESCRIPTION OF THE INVENTION

[0016] In FIG. 1, the filter regeneration system for eliminating particulate matter generated in a diesel engine includes a collected amount detecting unit 12 for detecting the amount of particulate matter collected in a filter and a temperature detecting unit 14 for detecting the temperature of exhaust gas discharged after combustion.

[0017] A control unit 16 determines the time to regenerate the filter based on the collected volume of particulate matter detected by the collected amount detecting unit 12. The control unit 16 also controls the time to inject the fuel and injection duration and amount necessary for incinerating the particulate matter collected in the filter 10 (FIG. 2) based on the time to regenerate and the temperature of the exhaust gas detected by the temperature detecting unit 14. A fuel supply unit 20 injects high-pressurized fuel into the exhaust system of a diesel engine 18 (FIG. 2) to promote combustion of the particulate matter. Control unit 16 preferably comprises a processor and memory, and other associated hardware and software as may be selected and programmed by a person of ordinary skill in the art to execute the control functions as described herein.

[0018] In FIG. 2, the collected amount detecting unit 12 monitors a filter 10 in an exhaust pipe 22 using pressure sensors 10 a and 24 a. Pressure sensors 10 a and 24 a are mounted upstream of an oxydation catalyst 24 a and downstream of the filter 10, respectively. Oxidation catalyst 24 reacts with the exhaust gas to raise the temperature of the exhaust gas, thereby contributing to combustion of the particulate matter. The control unit 16 determines the amount of particulate matter gathered at the filter 10 from the input values detected by the pressure sensors 10 a and 24 a and accurately determines a time to regenerate the filter 10 based on the amount of particulate matter collected by the filter 10. When the filter 10 has collected excessive particulate matter, the control unit 16 determines this time to regenerate the filter 10 by the increase in pressure between the pressure sensors 10 a and 24 a. One of ordinary skill in the art will know how to choose the pressure differential between sensors 10 a and 24 a that is used to trigger a regeneration.

[0019] The fuel supply unit 20 is composed of a fuel tank 28 filled with fuel with a fuel pump 30 mounted within for sending the fuel at a high pressure, and a secondary injector 34 connected via the fuel pump 30 and supply pipe 32, and mounted before the oxidation catalyst on the exhaust pipe 22. Intake air cooling device 42 cools intake air for diesel engine 18. A main supply pipe 44 provides fuel from the fuel tank 28 to the primary injector 36.

[0020] The temperature detecting unit 14 (FIG. 1) is a temperature sensor 26 mounted in the exhaust pipe 22 of the diesel engine 18 that detects the temperature of the exhaust gas. The control unit 16 determines the optimal amount of fuel necessary for incinerating the particulate matter accumulated in the filter from the temperature value of the exhaust gas detected by the temperature sensor 26.

[0021] Based on the difference between the temperature of the exhaust gas and the appropriate temperature for incinerating the particulate matter, the control unit 16 sends an appropriate signal to the fuel supply unit 20 so that unit 20 injects the amount of fuel necessary to raise the temperature of the exhaust gas to an optimal level for an optimal duration for incinerating the particulate matter. The control unit 16 causes the fuel supplied to the secondary injector 34 through the supply pipe 32 to be injected into the exhaust pipe 22. As a result, the fuel injected into the exhaust pipe 22 is ignited by the temperature of the exhaust gas and raises the temperature of the exhaust gas from 200° C.˜300° C. as much as 100° C.˜200° C., initially. The exhaust gas thereafter reacts with oxidation catalyst 24 and is heated to 550° C.˜600° C., which is an appropriate and preferable temperature for incinerating the particulate matter collected at the filter 10.

[0022] The control unit 16 increases the injected amount of fuel from the secondary injector 34, if the temperature of the exhaust gas circulating in the exhaust pipe 22 is low. If the temperature of the exhaust gas is high, the control unit 16 decreases the amount of the fuel injected, thereby preventing unnecessary fuel waste or decrease of the fuel combustion efficiency and engine output.

[0023] The control unit 16 is dedicated to the filter regeneration system and eliminating particulate matter generated in a diesel engine and is separate from a main control unit 40. Main control unit 40 is for controlling the operation of a primary injector 36, which is the injector mounted within the diesel engine for driving the engine. It is preferable to construct the control unit 16 as the exclusive control system for controlling the regeneration frequency, the amount of fuel injected to control incinerate temperature, and the injection duration. The purpose of this unique construction is to prevent the main control unit 40 from participating in the control of the filter regeneration system. This simplifies the control of the vehicle. Another purpose is to allow the filter regeneration system according to a preferred embodiment of the present invention to be installable separately from the existing construction, thereby enabling it to be an aftermarket installation without changing the existing main control unit 40.

[0024] As apparent from the foregoing, an advantage of the filter regeneration system according to the present invention, is that it accurately detects the time to regenerate and determines the amount of fuel to inject to eliminate particulate matter, thereby maximally reducing the amount of particulate matter discharged after combustion.

[0025] Furthermore, another advantage is that only a secondary fuel injection is used when regenerating the filter 10 and the control unit 16 is separate from the main engine control unit 41 thus simplifying the control logic and facilitating installation in a wider range of applications and thereby simplifying the control logic, dispensing with the development of an additional control unit for controlling an accurate control and providing an easy application.

[0026] The foregoing descriptions of specific embodiments of the present invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents. 

What is claimed is:
 1. A regeneration system for eliminating particulate matter generated in a diesel engine from a filter, the system comprising: a collected amount detecting unit for detecting the amount of particulate matter collected by a filter disposed in an exhaust system; a control unit for determining the time to regenerate the filter based on the amount of collected particulate matter detected by said collected amount detecting unit and for controlling an injection of fuel for incinerating the particulate matter; and a fuel injection unit mounted on the exhaust system for injecting the fuel into the exhaust system in response to the control of said control unit.
 2. The system as defined in claim 1 further comprising a temperature detecting unit for detecting the temperature of exhaust in said exhaust system, wherein said control unit controls the injection of fuel for incinerating the particulate matter collected by the filter based on the temperature of the exhaust gas.
 3. The system as defined in claim 1, wherein said collected amount detecting unit includes pressure sensors mounted downstream of the filter and upstream of an oxidation catalyst of the exhaust system.
 4. The system as defined in claim 2, wherein said temperature detecting unit is a temperature sensor disposed on said exhaust pipe.
 5. The system as defined in claim 1, wherein said fuel injection unit comprises: a fuel pump mounted in a fuel tank; and an injector connected via a supply pipe to the fuel pump and mounted at the fore end of said oxidation catalyst on said exhaust pipe.
 6. A method for regenerating a filter in an exhaust system of an engine, comprising: determining when to regenerate the filter; measuring the temperature of the exhaust; and increasing the temperature of the exhaust to regenerate the filter.
 7. The method of claim 6, wherein the determining comprises: measuring a first exhaust pressure from a point upstream of the filter; measuring a second exhaust pressure from a point downstream of the filter; calculating a pressure difference between the first and second pressures; comparing the pressure difference to a threshold pressure difference; and deciding to regenerate the filter if the pressure difference is greater than the threshold pressure difference.
 8. The method of claim 7, wherein the threshold pressure difference corresponds to the filter holding excessive particulate matter.
 9. The method of claim 6, wherein the measuring comprises measuring the temperature of the exhaust at a point upstream of the filter.
 10. The method of claim 6, wherein the increasing comprises injecting fuel into the exhaust to bring the exhaust near a desired temperature for a desired time.
 11. The method of claim 10, wherein the desired temperature and the desired time are a temperature and a time that result in incinerating substantially all a particulate matter from the filter.
 12. A system for regenerating a filter in an exhaust system of an engine, comprising: a detection system for detecting filter blockage and for determining when to regenerate the filter including a pressure sensor or a flow sensor; and an exhaust temperature increasing system, including an injector for injecting a combustible material into the exhaust system.
 13. The system of claim 12, the detection system further comprising: a first pressure sensor disposed in the exhaust upstream from the filter; a second pressure sensor disposed in the exhaust downstream from the filter; a control unit in communication with the first and second pressure sensors and programmed with instructions for: measuring a first exhaust pressure from a the first pressure sensor; measuring a second exhaust pressure from a the second pressure sensor; calculating a pressure difference between the first and second pressures; comparing the pressure difference to a threshold pressure difference; and deciding to regenerate the filter ifs the pressure difference is greater than the threshold pressure difference.
 14. The system of claim 12, the exhaust temperature increasing system further comprising a fuel injector for injecting engine fuel into the exhaust and a control unit in communication with the fuel injector, the control unit programmed with instructions for injecting fuel into the exhaust to bring the exhaust to a desired temperature for a desired time. 